Metal

Catalysis

Oxide

Electrochemistry

Materials science

Chromatography

Oxidation state

Transition metal

Biochemistry

In situ

Inorganic chemistry

Surface (topology)

Electrocatalyst

Physical chemistry

Redox

X-ray absorption spectroscopy

Physics

Nanotechnology

Organic chemistry

Crystallite

Mathematics

Optics

Surface reconstruction

Characterization (materials science)

Geometry

Analytical Chemistry (journal)

Crystallography

Chemistry

Electrode

Absorption spectroscopy

Journal of the American Chemical Society

The electrochemical CO2 reduction reaction (CO2RR) using Cu-based catalysts holds great potential for producing valuable multi-carbon products from renewable energy. However, the chemical and structural state of Cu catalyst surfaces during the CO2RR remains a matter of debate. Here, we show the structural evolution of the near-surface region of polycrystalline Cu electrodes under in situ conditions through a combination of grazing incidence X-ray absorption spectroscopy (GIXAS) and X-ray diffraction (GIXRD). The in situ GIXAS reveals that the surface oxide layer is fully reduced to metallic Cu before the onset potential for CO2RR, and the catalyst maintains the metallic state across the potentials relevant to the CO2RR. We also find a preferential surface reconstruction of the polycrystalline Cu surface toward (100) facets in the presence of CO2. Quantitative analysis of the reconstruction profiles reveals that the degree of reconstruction increases with increasingly negative applied potentials, and it persists when the applied potential returns to more positive values. These findings show that the surface of Cu electrocatalysts is dynamic during the CO2RR, and emphasize the importance of in situ characterization to understand the surface structure and its role in electrocatalysis.

Oxidation State and Surface Reconstruction of Cu under CO<sub>2</sub> Reduction Conditions from <i>In Situ</i> X-ray Characterization

Oxidation State and Surface Reconstruction of Cu under CO2 Reduction Conditions from In Situ X-ray Characterization

Oxidation State and Surface Reconstruction of Cu under CO₂ Reduction Conditions from In Situ X-ray Characterization